Minimizing the impact of data migrations on business operations is a critical part of storage management. Technology refresh requiring replacement of older servers or storage arrays with new ones is the major driver of physical data migration. Additionally or alternatively, either because of overall optimization considerations (e.g. CPU usage, memory availability, bandwidth, etc.) or because of configuration modifications (e.g. related to changes in user's privileges, etc.), a decision may come to migrate an application, thus requiring migrating data from one logical volume to another. Wide implementation of Virtual Machines and cloud technologies increases the need for data migration between logical volumes.
The problems of migrating data in the storage systems have been recognized in the conventional art and various systems have been developed to provide a solution, for example:
US Patent Application No. 2011/066597 (Mashtizadeh et al.) discloses a method of migration persistent data of virtual machines. The method includes the steps of copying the persistent data at the source data store to the destination data store, updating a bitmap data structure during the copying step to indicate which blocks of the persistent data have been modified during the copying step, identifying the blocks that have been modified during the copying step using the bitmap data structure, and copying the identified blocks to the destination data store.
US Patent Application No. 2010/299666 (Agbaria et al.) discloses a method for migrating a virtual machine (VM) in a computing environment. The method comprises receiving a request to migrate a VM executing on a source host to a destination host; defining a recovery point to which the VM is restored during recovery from a fault; and iteratively copying a memory of the source host associated with the VM to the destination host. During the copying, the original state of each page in the memory is preserved. At some point, the VM suspends executing on the source host, copies state information associated with the VM to the destination host, and resumes executing on the destination host. If a fault is detected on the source host, the VM is restored to the recovery point using preserved information.
US Patent Application No. 2007/192765 (Shimogawa et al.) discloses a virtual machine system managed by a current host OS virtually operating on hardware. A spare host OS is activated by copying the current host OS to a prescribed memory device using a live migration function when the current host OS is activated, notifies the spare host OS of a request issued to the current host OS via a virtual machine monitor, changes a state of the spare host OS, and switches an OS for managing the virtual machine system from the current host OS to the spare host OS, when the current host OS is in an erroneous state.
US Patent Application No. 2009/125904 (Nelson) discloses migration of a source virtual machine (VM) hosted on a source server to a destination VM on a destination server without first powering down the source VM. After optional pre-copying of the source VM's memory to the destination VM, the source VM is suspended and its non-memory state is transferred to the destination VM; the destination VM is then resumed from the transferred state. The source VM memory is either paged in to the destination VM on demand, or is transferred asynchronously by pre-copying and write-protecting the source VM memory, and then later transferring only the modified pages after the destination VM is resumed. The source and destination servers preferably share common storage, in which the source VM's virtual disk is stored; this avoids the need to transfer the virtual disk contents. Network connectivity is preferably also made transparent to the user by arranging the servers on a common subnet, with virtual network connection addresses generated from a common name space of physical addresses.
US Patent Application No. 2007/220121 (Suwarna) discloses a virtual machine migrated between two servers. A method, at the first server, dismounts a volume on which all the files relating to the virtual machine are stored, and which was previously mounted at the first server. The method, at the second server, mounts the volume on which all the files relating to the virtual machine are stored, so that the second server can host the virtual machine. In this way, the virtual machine can be migrated without having to copy all the files from the first server to the second server. The files relating to the virtual machine are stored on a storage-area network (SAN).
US Patent Application No. 2005/283564 (LeCrone et al.) discloses a method and apparatus for migrating one or more data sets each having one or more extents from one or more source logical devices to one or more target logical devices concurrently with interaction between the application and the data being migrated. A background operation copies each extent from the source logical device to the target logical device in a copy state. When a certain level of data has been copied, the extent is locked to assure synchronization of the data in the target logical device to the corresponding data in the source logical device. The status is changed to a mirrored state. When the extents for a data set in a source logical device or in a group of data sets have been mirrored, all the extents are changed to a diverted state. I/O requests to the diverted extents thereafter are intercepted and processed according to whether they access an extent that is in the copy, mirrored, or diverted state.
U.S. Pat. No. 6,145,066 (Atkin) discloses a computer system including a transparent data migration facility (TDNff) to accomplish automated movement of data (migration) from one location to another in the system. A data migration program includes a main module to control the start of a migration session when said application programs are using data accessed to and from the source volume, to migrate data from the source volume to the target volume, and to end the migration session whereby the application programs are using data accessed to and from the target volume. The data migration program includes a volume module to control the volumes during the migration session. The data migration program includes a copy module to control the copying of data from the source module to the target module during the migration session. The data migration program includes a monitor module for monitoring I/O transfers to the data volumes during the migration sessions. The computer system may have a plurality of operating systems associated with instances of the data migration program which allows for concurrent data migrations. The plurality of instances of the data migration program may also be controlled in a master slave relationship. A migration session may include a plurality of migration phases such as activation, copy, refresh, synchronize, redirect, resume and termination phases.